Method for boring parallel holes

ABSTRACT

A method for boring parallel holes in soft material such as earth, and more particularly for boring substantially parallel conduit runs in the earth between manholes or trenches, wherein a rod and piercing tool are rigidly spaced apart by a sharpened spacing element so that when the rod is forced through an existing hole, the piercing tool bores an additional hole substantially parallel to the existing hole.

United States Patent [191 Hicks et al.

[1 1 3,805,899 [451 Apr. 23, 1974 [54] METHOD FOR BORING PARALLEL HOLES [76] Inventors: Charles L. Hicks, 123 Henshaw Ave., Space 30; Raymond R. Leon, 123 Hensahw Ave., Space 8, both of Chico, Calif. 95926 [22] Filed: Mar. 29, 1972 [21] Appl. No.: 239,223

[52] US. Cl 175/19, 175/53, 175/62, 175/326, 173/45 [51] Int. Cl. E2lc 9/00, E210 23/00 [58] Field of Search 175/19, 22, 53, 61, 62, 175/326; 173/45 [56] References Cited UNITED STATES PATENTS 2,074,003 Y 3/1937 Templeton et al..... 175/53 X 2,698,169 12/1954 Fawkes 173/45 X 2,759,704 8/1956 Nemeth 175/22 2,903,252 9/1959 Ebeling 175/53 X 3,170,527 2/1965 Norton 175/326 3,451,491 6/1969 Clelland 175/53 X 3,482,641 12 /1969 Atkins et al. 175/62 X FOREIGN PATENTS OR APPLICATIONS 36,600 9/1967 Finland 175/326 Primary Examiner-David H. Brown Attorney, Agent, or Firm-Ernest L. Brown [5 7 ABSTRACT A method for boring parallel holes in soft material such as earth, and more particularly for boring substantially parallel conduit runs in the earth between manholes or trenches, wherein a rod and piercing tool are rigidly spaced apart by a sharpened spacing element so that when the rod is forced through an existing hole, the piercing tool bores an additional hole substantially parallel to the existing hole.

3 Claims, 19 Drawing Figures .rmgrmmm 23 I974 11805899 sum u 0F '6 E o y UN. g I 3 in? LL I l ill I I m PATENTEBAPR 23 I974 SHEET 6 [IF 6 fww METHOD FOR BORING PARALLEL HOLES BACKGROUND OF THE INVENTION It is customary, when forming bores, between manholes or trenches, for electrical conduit or utility pipes, to drive a substantially cylindrical piercing tool through the earth with a hydraulic ram. Typically the piercing tool is attached to a string of rods. That is, the piercing tool is forced into the ground by the ram. A rod is then attached to the trailing end of the piercing tool until only the end of the rod protrudes out of the ground. Another rod is then added to the trailing end of the embedded rod, and the process is repeated until the piercing tool reaches the other manhole or trench.

The piercing tool is then removed from the rod string, and an enlarging broach (called a frog) is attached to the end of the rod string. The enlarging broach is, typically, a conical member which, when forced through an existing hole, enlarges the hole to the diameter of the outer diameter of the broach. In the example, the enlarging broach is attached to the rod string with its smaller end facing the string. A conduit segment may be attached to the trailing or larger end of the broach. The rod string is then drawn back through the existing hole with the broach enlarging the hole to accommodate the conduit, and. the conduit following the broach. When the broach reaches the end of the hole adjacent the ram, the conduit thenextends between the manholes or trenches. If needed, additional segments of conduit may be spliced onto the conduit segment being pulled through the hole.

The process just described is particularly useful when it is desired to place a new conduit or utility pipe beneath existing pavement, as between existing manholes or from one side to the other of an existing street or highway.

It is obvious that the earth being penetrated must be sufficiently soft or granular to allow piercing. Most compacted roadbeds allow such piercing.

When it is desired to place more than one conduit, it is essential that the two conduit bores do not intersect. It is also desirable that they do not substantially diverge, for that would mean that future conduits would need to be spaced farther from the existing bores to avoid intersection.

Unfortunately, boring two holes substantially parallel using a piercing tool on the end of .a string of rods, as described above, is not adequately controllable, and it is the exception when two bores are substantially parallel.

BRIEF DESCRIPTION OF THE INVENTION The apparatus of this invention ensures that a second bore is substantially parallel to the first bore. A third bore may then be added parallel to the first two bores. Additional bores may be added as desired.

The apparatus contemplated by this invention is a tool for boring substantially parallel bores in relatively soft material, such as earth, clay, sand, gravel aggregates, road fabrication material, and the like.

The first or pilothole is bored, for example, as described above.

The apparatus of this invention has a first rod member which is contoured to be thrust into an existing bore. A piercing member is attached by a spacing member to the first ro'd member. In a preferred embodiment, the spacing member forms a knife edge which is inclined, like a guillotine knife, relative to the direction of travel of the piercing member.

After the first bore is completed, and before the rods of a first rod string in the first bore are pulled through the first bore with the enlarging broach to enlarge the first bore, the first rod portion of the tool of this invention is attached to the trailing end of the broach. The piercing member of the tool is positioned where the second bore is desired. A conduit segment may be attached to the trailing end of the first rod portion. Pulling of the first rod string by the hydraulic ram pulls the enlarging broach, the first rod portion of the tool, and the conduit through the first bore. At the same time, the piercing member of the tool is forced into the ground, forming a second bore substantially parallel to the first bore. As the piercing tool enters the ground,

a second rod string preferably is attached thereto. When the tool emerges adjacent the ram, the conduit will be in place in the enlarged first bore, and the second rod string will be in the second bore. The tool and broach, with the first rod portion of the tool positioned in the second bore, may then be used to pull conduit into the second hole while the piercing tool bores a third bore, parallel to the second and the first bores, pulling a third rod string after the piercing tool.

The parallel bores may be set into any desired configuration, i.e. side by side, in a vertical arrangement, or the like. Further, the spacing between bores may be adjusted by piercing one or more dummy bores to the side of the desired bores.

When it is desired to pull spliced flexible conduit, such as plastic conduit, into a bore behind the broach or behind the first rod member of the tool, the conduit typically cannot be pulled without pulling apart glued splices in the conduit. It is then, in accordance with this invention, desirable to snake a line through the conduit, attaching one end of the line to a bearing capon the trailing end of the spliced conduit and the other end of the line to the enlarging broach or to the trailing end of the first rod member of the tool, whereby the flexible conduit is pushed, rather than pulled, into the conduit bore. It is desirable to have a centering member on the trailing end of the broach or first rod member to center the'pull of the line along the axis of the conduit. A preferred centering member comprises a ball-like fitting on the leading end of the conduit, and a matching cup on the trailing end of the first rod member of the tool or on the enlarging broach. The line is preferably attached at the center of the cup and penetrates through the center of the ball-like fitting into the conduit.

With the apparatus of this invention, a slice is made by the spacing member between adjacent bores, but the spacing member is not followed by any other member to hold open the slice. When the hole is enlarged by the enlarging broach, the sliced portion is re-compacted.

When flexible conduit has been placed in an adjacent bore prior to the enlarging by the broach, it is desirable to'use a special broach of this invention. Alternatively, a fitting or mantle may be placed over the broach, the mantle having special characteristics to prevent crushing of the emplaced conduit. The special broach will be described herein as aspecial mantle which fits over the broach. The special broach or broach mantle has a second blade or stress reliever thereon which is substantially in a plane tangential to the enlarged bore, whereby stress in the earth, created by the enlarging broach, is directed away from the stress reliever. The stress reliever is preferably placed on the side of the broach or broach mantle adjacent the emplaced flexible conduit. The size of the stress reliever is adjusted so that sufficient compacting stress is directed toward the slice made by the spacer to compact the slice.

The broach mantle is adjustably positioned on the leading end of the first rod member, over the broach, so that the stress-relieving blade is positioned on the side of the bore toward the emplaced flexible conduit. The second blade is held in position by preventing the broach mantle from turning about the axis of the bore during the enlarging process. To prevent the turning, the trailing or large end of the broach mantle has a plurality of axially directed tines thereon, two of which straddle the spacing member.

It is a first process of this invention to (l) pierce a hole, drawing a rod string into said hole, and (2) pierce a second hole, holding the piercing member a fixed distance apart from said first hole, using the emplaced rod string as a guide for the piercing member.

It is a second process of this invention to (l) pierce a hole, drawing a rod string into said hole, and (2) enlarge said hole while piercing a second hole, holding the piercing member a fixed distance apart from said first hole, using the emplaced rod string as a guide for the piercing member.

It is a third process of this invention, in addition to the steps in the next above paragraph, to draw a second rod string into said second hole as said second hole is pierced.

It is a further process of this invention to pierce two parallel holes by l piercing a first hole, drawing a rod string into said first hole, (2) piercing a third hole, parallel to said first hole, drawing another rod string into said third hole, and (3) piercing said second hole, parallel to said third hole.

It is a more particular process of this invention to enlarge a first hole and pull conduit therethrough while simultaneously piercing a second hole parallel to said first hole, using said first hole as a guide for said second hole.

It is an extended process of this invention to continue the above processes to pierce additional holes parallel to the first and second holes.

It is therefore an object of this invention to pierce parallel holes in materials.

It is a more particular object of this invention to pierce, enlarge, and pull conduit or utility pipe into parallel holes.

It is still a more particular object of this invention to provide apparatus and methods for achieving the above-enumerated objects.

More particularly it is an object of this invention to provide a tool for boring parallel bores, particularly through compacted earth, and the like.

BRIEF DESCRIPTION OF THE DRAWINGS Other objects will become apparent from the following description, taken in connection with the accompanying drawings, in which:

FIG. 1 shows a piercing tool, rod string, and forcin apparatus such as a hydraulic ram, according to the prior art;

FIG. 2 shows a first embodiment of the invention in place, ready to form a second bore parallel to the first bore;

FIG. 3 shows the apparatus of FIG. 2 during the process of forming the second bore, enlarging the first bore, and pulling conduit into the first bore;

FIG. 4 shows conduit in place in the first bore, the third bore being pierced, and the second bore being enlarged while conduit is being pulled into the second bore;

FIG. 5 shows an alternative embodiment of FIG. 4 wherein the enlarging broach carries a special mantle, and the conduit coupling mechanism is adapted for use with flexible conduit;

FIG. 6 shows the apparatus of this invention boring holes without the enlarging broach;

FIG. 7 shows an exploded view of a typical tool in accordance with this invention;

FIG. 8 shows a typical conduit run wherein the parallel conduits are of varying size;

FIG. 9 is a figure to demonstrate how variably spaced bores may be formed with the tool of this invention;

FIG. 10 shows a typical conduit run of identically sized holes or bores;

FIG. 11 is a view, partly in section of the apparatus of FIG. 7 assembled;

FIG. 12 is a view, taken from the bottom in FIG. 11;

FIG. 19 is a view of a conduit attachment for flexible utility pipe.

DETAILED DESCRIPTION OF THE INVENTION FIG. 1 shows a prior art device for boring conduit holes, for example, between two trenchesor manholes 20,22. A piercing tool 24 is forced into the ground 26 by a forcing mechanism such as a hydraulic ram 28. Typically a plurality of rods 30 are attached to the trailing end of the piercing tool 24. As the piercing tool penetrates deeper, additional rods 30 are added to the g string until the piercing tool 24 reaches the trench or manhole 22.

The piercing tool 24 is removed from the string of rods 30, and the tool 32 of this invention is attached to the end of the string of rods 30 to be pulled back through the first bore.

The tool of this invention, as shown in FIGS. 2 and 3, comprises a first rod member portion 34 and a piercing tool 36 attached by a spacing member 38 to the rod member 34. The spacing member 38 is, typically, a sheet of steel with a wedge blade 40 on its leadingedge. The blade 40 is preferably tilted relative to the direction of motion of the apparatus 32 so that the blade 40 slices the earth 26. The tilt of the blade 40 causes the spacer 38 to be similar to a guillotine blade. The spacer 38 is preferably as thin as possible while still maintaining its rigidity of spacing.

sitioned to start a new hole in the wall 42 of the trench or manhole 22.

An enlarging broach 44 is attached to the string of rods 30 and to the tool 32, as shown. The broach 44 (sometimes called, in the trade, a frog) is substantially conical in shape, having a smaller diameter, atthe contact with the rods 30, substantially equal to the diameter of the rods 30. (It should be noted that the piercing tool 24 may have the same diameter, or slightly larger, as the rods 30). The larger diameter of the broach 44 is sufficiently large to create a bore accommodating the conduit or utility pipe 46. The conduit or utility pipe 46 is preferably attached to the trailing end of the rod member 34.

As the rods 30 are drawn back toward the ram 28, the tool 32 is also drawn toward the ram 28. The broach 44 enlarges the first bore, and the conduit or pipe 46 is drawn into the enlarged bore. The piercing member 36 pierces a second bore substantially parallel to the first bore, and the spacer 38 cuts a slice 48 between the bores 50,52. The slice 48, however, is not held open and the dirt fills in slightly behind it. Compaction of the bore 52 on the next pass of the tool 32 completes the compaction of the slice 48, completely filling it. A second string of rods 54 is pulled behind the piercing member 36.

During the cutting of the earth by the tool 32, the resistance of the earth 26 to the piercing tool 36 produces a torque, about an axis perpendicular to the sheet of the FIG. 3, to be placed on the tool. The torque is resisted by the string of rods 30 in the first bore, and the apparatus moves through the earth without binding.

FIG. 4 shows how the second bore may be used to guide the tool 32 through the ground 26 to form a third bore 60 which is substantially parallel to the second bore 52 and, hence to the first bore 50.

It should be noted that, as shown in FIG. 8, the different bores in a conduit run may be of different size. The bores may be formed with different sized broaches 44 or with no broach at all in the smallest size.

It should be noted, as shown in FIG. 9, that the spacing between adjacent usable parallel bores 126,127 may be varied by forming one or more auxiliary bores such as 128. The bore 126 may be formed first. The bore 128 is formed next. Then the bore 127 is formed parallel to the bore 128. The spacing between bore 126 and bore 128, and the spacing between bore 128 and bore 127 is the length of the spacer element 38. Note, however, that the spacing between bore 126 and bore 127 may vary up to a dimension equal to twice the length of the spacer element 38. The unused bore 128 is usually compacted by the broach being pulled through the bore 127.

If the spacing between bores 126 and 127 is desired to be greater than twice the length of 'the spacer element 38, additional unused bores (not shown) can be formed between the bores 126 and 127.

When a bore is to be unused, preferably an entire rod string is not pulled behind the rod member 34 of the tool. Instead, as shown in FIG. 6, a single rod 86 is used I to counter the torque on the piercing member 32.

A typical conduit run of six identical bores is shown, by way of example, in FIG. wherein the bores are formed in sequence l31,132,l33,134,'135,136.

FIG. 5 shows the tool of this invention in combination with apparatus for pulling flexible conduit and a special broach mantle with a novel stress reliever 72.

When a spliced plastic conduit is used, it is preferable not to pull in the conduit, but to push it. Such a flexible conduit is attached to the tool 32 by a cable or other flexible tension member 76. The cable 76 extends down the central axis of the conduit 74, and it is attached to a bearing cap 78 on the trailing end of the conduit 74. Motion of the tool 32 pulls the cable 76 and the bearing cap 78 which pushes the flexible conduit 74. The conduit 74 is centered on its leading end by a 'ball centering cap 80 which fits into the leading end of the conduit 74. A matching cup 82 is attached to the trailing end of the first rod member 34. The cable 76 is preferably attached to the center of the cup 82 and extends through a central aperture 81 (See FIG. 17) in the ball cap 80.-

The basic tool 32 is shown in exploded view in FIG. 7. In FIG. 7, the string of rods 30 screw onto the leading end of the conical broach or frog 44. A coupling screws onto the stud 92 on the trailing end of the broach 44. The rod member 34 comprises a rod 94 which screws into the coupling 90 and the coupling 96. The rod 94 forms a sliding fit into the sleeve 98 so that the angular position of the piercing member 36 about the axis of the rod member 96 is adjustable, allowing choice in positioning before a bore is commenced. The

conduit coupler 100 is adapted to grasp a conduit or utility pipe 46, as by screw threads. On the forward end of the coupler 100, anear 102 fits between a pair of matching ears 103,104. A pin 105 (FIG. 11) is adapted to fit into the transverse holes in members 102,103,104 to carry the pull on the coupler 100.

The piercing member 36 is attached to the sleeve 98 by a spacing member 38 which keeps the piercing member 36 a fixed distance from the sleeve 98 and causes the bore being formed to be substantially paral-. lel to the existing bore which carries the rods 30. The leading edge 40 of the spacer 38 is sharpened to a wedge to penetrate the earth. The blade 40 may be substantially perpendicular to the axis of the bore of the rods 30, but it is preferably angled, after the fashion of a guillotine, as shown in FIG. 11, relative to the direction of traVel of the tool 32, to aid in slicing the earth.

The leading end 41 of the piercing tool 36 is pointed to penetrate the ground. The trailing end of the piercing member 36 carries ears 108,109 which straddle the ear 110, on the leading end of coupler 112, to which they are attached. The assembled tool 32 is shown in FIGS. 11,12,13.

An embodiment of the broach mantle of this invention for use to prevent damage to flexible conduit in adjacent bores is shown in FIGS. 14,15,16. The mantle 70, preferably made of rigid material such as metal, fits like a skin over the broach 44. The broach 44 has a threaded stud projecting from its leading or small end, and a coupler screws onto that stud 140, holding the mantle 70 onto the conical broach 44 and for attachment to the string of rods 30. A stress reliever 72 is attached by a plate 142 to the mantle 70. The stress reliever 72 is a plate which is tangential to the enlarged bore formed by the broach mantle 70. Stress in the earth, caused by the forcing of the broach mantle 70 through the earth, is directed away fromthedirection of the plate 72, whereby flexible conduit in adjacent bores, in the direction of the plate 72, are protected. To

aid the stress reliever 72 and the attaching portion 142 in penetrating the earth, the leading edges 144,!46 are sharpened into blades.

To prevent the breach mantle 70 and the plate 72 from turning, during use, about the axis of the rods 30, bifurcated pairs of tines l50,l51,l53,154,156,157 are directed axially from the trailing end of the mantle 70 and spaced apart to straddle the spacer element 38 as shown particularly in FIGS. 14 and 15. Two positions of the mantle 70 and stress reliever plate 72 are shown in FIG. 15. The dotted lines 36a and 38a show a second position of the piercing member 36 and the spacer 38 relative to the mantle 70.

The bearing cap 78 for the flexible conduit 74 is shown in detail in FIGS. 17 and 18. The cap 78 has a slot 159 formed therein through which the cable or chain 76 extends. The cable or chain 76 is snubbed on the upstanding tab 160.

The cap 80 for the leading end of the flexible conduit 74 is shown in FIG. 17. It has a ball surface 170 on its leading end. The ball surface 170 is perforated on the axis of the conduit 74 to allow the cable or chain 76 to extend therethrough.

Recently utility pipe is available in flexible rolls. A typical pulling coupler which may be used to pull in flexible pipe is shown in FIG. 19. The coupler fits into the interior of a flexible pipe 190. A loop 191 on the leading end of the coupler is adapted to be pulled. The loop 191 is connected to a bolt 192 which extends axially through a plug 193. The interior end of the bolt 192 is attached to a bearing plate 194. A resilient (such as rubber) collar 195 is positioned between the plug 192 and the plate 194, whereby pulling on the loop 191 and bolt 192 causes the plate.194 to compress the collar 195 which frictionally grips the inner wall of the pipe 190.

It may therefore be seen that with this invention, precisely parallel bores may be formed through compacted materials for cmplacing conduit and utility pipe.

The invention further contributes particular structure and method for pulling in rigid and flexible conduit and pipe while forming parallel runs for each conduit and pipe.

Particular structure of the tools allows enlarging of the bores while piercing new, parallel bores, protecting emplaced flexible conduit, and the like.

With the apparatus and method of this invention, conduit and utility pipe may rapidly be emplaced under streets and between manholes, materially-reducing the cost of such operations while producing a better quality run.

Although the invention has been described in detail above, it is not intended that the invention should be limited by that description, but only by that description taken together with the appended claims.

I claim:

1. A method for forming a bore parallel to and spaced apart from an existing bore, having a rigid member therein, comprising:

pulling a piercing tool through the material to be bored; while continuously guiding said piercing tool in predetermined fixed spacing apart from said rigid member.

behind said piercing tool. 

1. A method for forming a Bore parallel to and spaced apart from an existing bore, having a rigid member therein, comprising: pulling a piercing tool through the material to be bored; while continuously guiding said piercing tool in predetermined fixed spacing apart from said rigid member.
 2. The method of claim 1 and further comprising: applying a torque on said piercing tool, about an axis perpendicular to the plane of said bores, to prevent said piercing tool from converging toward and diverging from said rigid member.
 3. The method of claim 2 and further comprising: pulling a second rigid member in said second bore behind said piercing tool. 